page itself:

so I pulled tree into separate folder, switched to branch, extracted 3 last commits, git am them to ffmpeg.git (there was host copy vulkan fix in meantime)

And ....

it seems to work.

At least for HQ profile ... 

at 4.5 fps, but this is faster than ffv1 (but not lossless, obviously).

./ffmpeg  -init_hw_device vulkan=vulkan -hwaccel vulkan -filter_hw_device vulkan -i /dev/shm/Nature072-A006C0035_230328_4U1Q.mov -vf libplacebo  -c:v prores_ks_vulkan -f matroska -noautoscale -pix_fmt vulkan  4k.mov
ffmpeg version N-120782-gc12bca52f8 Copyright (c) 2000-2025 the FFmpeg developers
  built with gcc 11.2.0 (GCC)
  configuration: --enable-opencl --disable-debug --enable-libx265 --enable-libx264 --enable-gpl --enable-libplacebo --enable-vulkan --enable-libshaderc --enable-libzimg --enable-libaom --enable-libdav1d --enable-libsoxr --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-gnutls --enable-libass --enable-libbluray --enable-libcdio --enable-frei0r --enable-libgsm --enable-openal --enable-libopus --enable-librtmp --enable-libsnappy --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libv4l2 --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp
  libavutil      60. 19.101 / 60. 19.101
  libavcodec     62. 21.100 / 62. 21.100
  libavformat    62.  6.103 / 62.  6.103
  libavdevice    62.  2.100 / 62.  2.100
  libavfilter    11. 10.101 / 11. 10.101
  libswscale      9.  3.100 /  9.  3.100
  libswresample   6.  2.100 /  6.  2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/dev/shm/Nature072-A006C0035_230328_4U1Q.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 512
    compatible_brands: qt
    creation_time   : 2023-04-07T18:41:32.000000Z
    encoder         : Blackmagic Design DaVinci Resolve Studio
  Duration: 00:00:08.00, start: 0.000000, bitrate: 1787424 kb/s
  Stream #0:0[0x1]: Video: prores (HQ) (apch / 0x68637061), yuv422p10le(tv, bt709, progressive), 3840x2160, 1787418 kb/s, SAR 1:1 DAR 16:9, 60 fps, 60 tbr, 15360 tbn (default)
    Metadata:
      creation_time   : 2023-04-07T18:41:32.000000Z
      handler_name    : VideoHandler
      vendor_id       : appl
      encoder         : Apple ProRes 422 HQ
      timecode        : 21:22:52:12
  Stream #0:1[0x2](eng): Data: none (tmcd / 0x64636D74), 0 kb/s
    Metadata:
      creation_time   : 2023-04-07T18:41:32.000000Z
      handler_name    : TimeCodeHandler
      timecode        : 21:22:52:12
File '4k.mov' already exists. Overwrite? [y/N] y
Stream mapping:
  Stream #0:0 -> #0:0 (prores (native) -> prores (prores_ks_vulkan))
Press [q] to stop, [?] for help
[prores_ks_vulkan @ 0xb299440] Autoselected HQ profile to keep best quality. It can be overridden through -profile option.
Output #0, matroska, to '4k.mov':
  Metadata:
    major_brand     : qt
    minor_version   : 512
    compatible_brands: qt
    encoder         : Lavf62.6.103
  Stream #0:0: Video: prores (HQ) (apch / 0x68637061), vulkan(tv, bt709, progressive), 3840x2160 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 60 fps, 1k tbn (default)
    Metadata:
      encoder         : Lavc62.21.100 prores_ks_vulkan
      creation_time   : 2023-04-07T18:41:32.000000Z
      handler_name    : VideoHandler
      vendor_id       : appl
      timecode        : 21:22:52:12
[out#0/matroska @ 0xb29ddc0] video:1770722KiB audio:0KiB subtitle:0KiB other streams:0KiB global headers:0KiB muxing overhead: 0.001071%
frame=  480 fps=4.5 q=-0.0 Lsize= 1770741KiB time=00:00:08.00 bitrate=1813239.1kbits/s speed=0.0755x elapsed=0:01:45.90

testing:

bash-5.1$ mplayer 4k.mov
MPlayer SVN-r38660-11.2.0 (C) 2000-2024 MPlayer Team
227 audio & 468 video codecs
do_connect: could not connect to socket
connect: No such file or directory
Failed to open LIRC support. You will not be able to use your remote control.

Playing 4k.mov.
libavformat version 61.6.100 (internal)
libavformat file format detected.
[lavf] stream 0: video (prores), -vid 0
VIDEO:  [apch]  3840x2160  0bpp  60.000 fps    0.0 kbps ( 0.0 kbyte/s)
==========================================================================
Opening video decoder: [qtvideo] Quicktime Video decoder
sh->ImageDesc not set, try -demuxer mov if this fails.
QuickTime6.3 DLLs found
QuickTime.qts patched!!! old entry=0x6693c3e0
theQuickTimeDispatcher catched -> 0x6693c3e0
WARNING! Invalid Ptr handle!
theQuickTimeDispatcher catched -> 0x6693c3e0
theQuickTimeDispatcher catched -> 0x6693c3e0
Movie-Aspect is 1.78:1 - prescaling to correct movie aspect.
VO: [vdpau] 3840x2160 => 3840x2160 Packed YUY2
DecompressSequenceBegin result=-8961
VDecoder init failed :(
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
libavcodec version 61.17.100 (internal)
Selected video codec: [ffprores] vfm: ffmpeg (FFmpeg Apple ProRes)
==========================================================================
Clip info:
 COMPATIBLE_BRANDS: qt
 MAJOR_BRAND: qt
 MINOR_VERSION: 512
 ENCODER: Lavf62.6.103
Load subtitles in ./
Audio: no sound
Starting playback...
Could not find matching colorspace - retrying with -vf scale...
Opening video filter: [scale]
Movie-Aspect is 1.78:1 - prescaling to correct movie aspect.
[swscaler @ 0x57a10180]bicubic scaler, from yuv422p10le to yuv420p using MMXEXT
VO: [vdpau] 3840x2160 => 3840x2160 Planar YV12
[VD_FFMPEG] DRI failure.
Movie-Aspect is 1.78:1 - prescaling to correct movie aspect.
VO: [vdpau] 3840x2160 => 3840x2160 Planar YV12
V:   0.0   0/  0 ??% ??% ??,?% 0 0
[VD_FFMPEG] DRI failure.
V:   0.3   0/  0 ??% ??% ??,?% 0 0
[ASPECT] Warning: No suitable new res found!
[ASPECT] Warning: No suitable new res found!
V:   1.9   0/  0 47% 460%  0.0% 0 0

Exiting... (Quit)

I wonder if Terje can replicate those results? Do not forgot to check if libplacebo was compiled in for your ffmpeg version ...